Voltage regulator



Aug: 19, 1952 A. O. BUNBLASKY ET AL VOLTAGE REGULATOR Filed Sept. '7.1951 ATTORNEY Patented Aug. 19, 1952 VOLTAGE REGULATOR Adolph 0.Bunblasky, New Canaan, and Allen K.

Brown, Stamford, Conn., assignors to Sorensen & Company, Inc., Stamford,Conn., acorpora tion of Connecticut Application September 7, 1951,Serial No. 245,538

13 Claims.

rThis invention `relates to new Yand useful 'improvements in voltageregulators and Vhas particular relation to a regulator for controllingthe voltage from an alternating'current power sur ply so that saidvoltage remains virtually constant over a relatively wide rangel ofypredeterminable voltages.

In general, the present .regulator includes a bridge type networkvhaving `a diode vacuum tube forming one of the arms of the bridge. Theiilament of the diode is connected across the output of thevoltage'regulator whereby the temperature of the :filament changes inresponse to changes in the output volta-ge; This temperature change thenresults in a change in the plate resistance of the diode ,and asubsequent imbalance of the bridgecircuit.. The output ci the bridge isthen fed through a filter network in order to reduce any componentripple -voltage and is used to control thev output from the first stageof a cascaded amplifier. The output from the first stage is fed througha ,second filter network into the second. stage.

` The output Afrom the cascaded amplier is then fed throughanotherfilter circuit lwhich nulliiies any tendency for the circuit tohunt and is then appliedto the icontrolgrid of another vacuum tube. vThevplate current ofthis latter tube is fed through the direct currentwinding or" a saturable core reactor in order to control the impedanceof Vthealternating fcurrent Winding. As this Winding .is in series-iwith a 4lead common to the input'circuit'and Voutput circuit of theregulator, the -voltageis varied in accordance with the impedance ofthealternating current winding. Thus, the output ofthe regulatorapproximately i .01% against variations ldue v from any of the vacuumtubesl include'din the circuit fail, the `output voltage would tend todrop rather than rise therebyprotecting any Iter-minal 23.

equipment fed lfrom the output `from' being damaged by excessivevoltage.

Another object is to provide a highly stable voltage regulator meetingthe above objects and also providing a virtuallydistortionlessalternating current output.

Still another object is to provide a highly stable voltage regulatoradapted to start even under large loads.

The above and other objects of the'invention will become apparent from aconsideration oi the following detailed description taken in con`nection with the accompanying drawing wherein a satisfactoryembodimentof the invention is shown. However, it vis to vbe understoodthat the invention is not limited to the details disclosed but includesall such variationsand Amodiiications as fall within the spirit of the.in've'n-rv tion and the scope of the appended claims;

In the drawing 'the `iigure represents a schematic diagram'ooneembodiment of the ,invention.

Referringin detailftothefdrawing, an alternating currentinput is appliedto `a pair o'finput terminals Ii] and `II and is thence fed through apair of contacts I2 and I3 of'onoi switch I4. The side of -the'lineconnected to the yterminal IU through the switch vContact I2 is con-`nected directly to atapVV I5on an auto-transformer Ithrough -a lead-I2a. The other "sideof theline, i.,e., that connected tothe terminal IIthrough the switch contact I3, is fed by aconnection I'I through .thealternating current windings vI8 and I9 0i a saturable ycore'ireactor2.6, which also has a direct currentvwindin'g r2I, to a terminal 22 ofthe'.auto'transiormer Iii. Thus, the alternating curre'rit windings ISand i9 lare in series with lthe connection Il forming part of a feedline to the auto-transformer `I G;

The alternating` current output'is developed across the youter ends ofthe auto-transformer i6 and appearsacross thefterniinal 22 and aThe-terminal V23 lis `carried by ra connection 24 through a`thermal-overload switch 2-5-to an outputiterminal 26. Anotheroutput-terminal 2'I is'connectedfdirectly tothe connection I'I'by-meansof aleadB.'

Inorder to filter outany third harmonic distortion whichmight beotherwise present at lthe output,=a lnetwork comprising a pair ofcapacitors 29 and l3B andan inductance 32 is.provided. Thecapacitor-staand 3a are connected' in parallel and this combination isthen connected in series with the inductance 32 across the 'output'lines formed bythe connections `I'I and 24.' 4In order to lter `outariy'iiithv harmonic distortion, a

aeozoia filter comprising a series combination of a capacitance 33 andan inductance 34 is also connected across the connections 25 and I1. Aninductance 35 is placed across the terminals 25 and 21 in order toprovide an inductive load so as to make the regulator capable ofhandling loads with a capacitive power factor.

A transformer 36 is associated with the control circuit presently to bedescribed in detail. The primary 31 of the transformer 38 is connecteddirectly across the output terminals 26 and 21. An end terminal 38 isconnected through a fuse 39 to the output terminal 25. Another endterminal 48 is directly connected by a lead comprising the sections 4I,42, 43, 44 and 45 to the other output terminal 21.

A secondary 45 of the transformer 35- is connected directly across theplates 41 and 48 of a rectifier tube 48. Another secondary I isconnected across the filament 52 of the rectifier tube 49 to provideheating current therefor. A direct current voltage is thus developedacross a terminal 53 associated with the filament 52 and a center-tap 54on the secondary 45. This voltage has, of course, a decided ripple whichis effectively reduced by a capacitor 55 and a resistance 55 connectedacross the terminal 53 and the center-tap 54. Resistance 55 also servesas a voltage divider to provide voltage of a proper value for the screengrid 51 of a vacuum tube 58.

The vacuum tube 58 is associated with the control circuit hereinafterfully described. Briefly, however, the plate current from the vacuumtube 58 is fed through the direct current winding 2! of the saturablecore reactor 28 to control the impedance of vits alternating currentwindings I8 and I9.

Plate 59 of the vacuum tube 58 is connected through a load resistance 60to the terminal 53 of the rectifier 48. The direct current Winding '2lis connected in parallel with the load resistance 55. The negativeterminal of the rectified supply, as represented by the terminal 54, isconnected directly to a cathode 52 of the vacuum tube 58. A bleederresistance 6I is provided between the plate 59 and the screen grid 51.

former 55 is connected between the terminals 23 and I5 of theauto-transformer I6. The secondary winding 65 in series with thesecondary Winding 54 acts as a booster which enables the regulator tostart even under large loads.

By way of example, assuming a load of 1000 volt-amperes and a voltageinput to the regulator of only 95 volts, if the unit is then turned onby closing the on-off switch I4, the voltage across the secondary 64 ofthe transformer 35 may be so low as to prevent the filament 63 fromheating. By providing the secondary winding 55 of the boostertransformer 56, the voltage across the filaments will be sufficient toallow the vacuum tube 58 to heat up and thereby make the control circuitoperative. Once the control circuit operates, the normal filamentvoltage is developed across the filament 63.

The principle of booster transformer 66 is that the difference betweenthe input and the output voltage is impressed on the primary of thistrans- 4 former. When the control circuit is not operating, thisdifference is relatively large and thus applies a correspondingly largeboost to filament 53. Once the control circuit operates, the differencebecomes small and a very negligible, if any, boost is applied tofilament 63.

A Wheatstone type bridge circuit comprising arms formed by resistances10,' 1I, and 12 and a diode vacuum tube 13 is provided in order todetect changes in the voltage across the output terminals 25 and 21. Thediode vacuum tube 13 is preferably a special diode, as fully describedin l a copending application of Helterline et al. en-

titled Filament Failure Device for Electronic Tubes filed April 1, 1949,under Serial Number 84,806. This diode has the characteristic thatshouldthe tube fail for any reason, the filament is shorted to theplate. This is illustrated schematically in the figure by an arm 14connected to a plate 15 of the diode 13, said connection being withinthe envelope of said diode. Upon failure of the tube, due to itsfilament 16 burning out, arm' 14 comes in contact with the filament 16of the diode 13, thereby shorting said plate 15 to the filament 16.

Although a conventional diode may be used in place of the special diodedescribed, it is preferable to use such a special diode as a safetyprecaution. By way of example, upon failure of thespecial diode 13, theshort circuiting of the plate and filament results in a decrease in theoutput voltage across the terminals 25 and 21. This is of importance ifequipment sensitive to high voltages is being supplied by the regulatedoutput. If a conventional diode were used, the output voltage would tendto`rise with possible silibsequent damage to the equipment being suppied.

One side of the filament 16 is connected by a lead 11 through a pair ofserially connected dropping resistances 18 and 19, thence by a lead 8|to a movable pole 82 of a single pole double throw switch 83. A contact84 of the switch 83 is connected to a variable resistance 85. The othercontact isconnected to a second variable resistance 81 and the two endsof the variable resistances 85 and 81 are connected to a lead 88. Thus,when the movable pole 82 is against contact 84, leads 8I and 88 areconnected together through the variable resistance 85. In a similarmanner, when the movable pole 82 is against contact 86, the leads 8| and88 are connected together through the variable resistance 81. By meansof the switch 83 and the variable resistances 85 and 81, the filamentcurrent may be varied in order to adapt the circuit for operation over awide range of desired output voltages.

Lead 88 is connected to the lead 4I and thence to the terminal 48associated with the primary 31 of the transformer 36. The other side ofthe filament 16 is connected through a lead 98 thence by a lead QI tothe terminal 38 of the primary Winding 31. As the voltage across theterminals 38 and 40 is the same as that across the outputs 26 and 21, itis evident that the filament 16 is likewise across the outputs and itstemperature and hence emission will vary with changes 'azionare theoutput terminal 21. y The terrn'inaffljicon- Iiooted through thetub.socketfoithedodo 13 so that in theevent the diode 1 3 is vren 1oyed one side ofl the linev to the'primaryjof the trans- .former 92` and theprimary 31 of the transformer 3|.`is automatically opened.

. This' results 4in Vthe .power supply includingthe :diode 49 beingdeenergizedthus rQmQYIlg plate voltage from the'yacuumjtube 5 8...'Iherexfcre. the current' through the direct current winding 21 of thesaturable core reactor 20 `is reduced tozero and the impedanceof the'alternating current portions 18 and I9 increases to reduce' the voltageacrossthe'output terminals 26 and 21. As mentionedin connectiomwiththe'description of the diode 13,'this is an important. safety feature.for protecting .any sensitivexequipment fed from the outputterminals"26"an d21..

A secondary winding102 of the .transformer 92 .provides a Voltage supplyfor the bridge circuit.

The alternating current developed across the secondary 1 02Lis rectifiedby a suitablefrectier l|113 which may be of the selenium, copper voxideor, in fact, of .any convenient type. Qne side ofthe 'rectifierf103isconnectedtoa terminal 104er the secondary102 and the other side isconnected throughfa resistance |05 1and a resistance 1135 .toaninputterminal 101 Qf the bridge circuit.

.The other terminal 1.08 of thesecondarywinding |02 is ,connecteddrectly to another input terminall of the'bridge circuit. A capacitor116 is connected from the terminal |08 to the junctionof theresistancesl|115 and |0 6.

The capacitance, in conjunctij on with the resistance A1 (15, servesas afilter network Ato smooth out thoroctihor, ripple ,and .the .resistance106 ...serves aspart-oiavo1taee divider .to predotormiho the voltageacrossthe bridge input terminals |01 and 10.9. Neontubes, 1 1 1 112,113) and |14 are lconnected across the inputterrninals |01 and 10Q,.to..f urther .stabilize theroltoeo applied to the bridge, As theprimary 9 3 of the transformer 92 .is ...connected-V ooross .the.regulated output termi- .,nels'ahd ,2.1. the .output of .thorootor H13iS quite stable but, by providingthe neon tubesstill v further voltagestability is achieved, A constant input voltage to the bridge circuitAinsures that the ontput of the bridge `will yary onlyq in Aaccordance vwith changes in the impedance of the vacuum tubo 1 3.

An increase in the'voltagehwillMcausethe'nlanient 1 6 of the diode 13 toincreaseintempera- .turewith a resulting increase inemissiornwThiscauses the impedance of the diode 13 to decrease andaresultingunbalance' in the bridge. This .uhbalehoo .further ,results.ih o choose. in. the yoltageappearing across a pairof bridge outputterminals |5 and |13 causing theterminal |15 .to become more negativewith respect to the terminal-A 1 16.

r The output yoltagedeveloped theoutput terminals |15 and `11|; of thebridge circuit is applied to a filter network I 1"!A connected'betweenacontrol grid 1 i8 anda cathode 19 of a dual vacuun1tub e 120. Thefilter network |11 comprises two'serially connected4 capacitors 23 and.124 Aconnected in parallel with a resistance |25. The resistance isconnected between the bridge O utputterminal |15 and the control grid 118. A resistance |26 is connected between the j''nction of the seriallyconnected capacitors |23 and |24' and the cathode 19 of the vacuum tubel greatly attenuate any 120 cycle ripple appearing tutti@ for thebridge. "The izo cycle 'ripple' is introduced in the`- ley""virtueA ofthe` 'full Wave powersupply 'comprising' the transformer' 3B and thedualftriode yacuumftbelil. An addi- "tota no' colocataires@ throated theCircuit due L to the ytlfierrnal effectI of the diode filament. Byattenuati athis ripple, the voltage 10 cathode ,l le .is olisthiitodloot @destron- .ago oxoootfore Spoil@ oyclerpplemtroduced plenairQ ftiie' vacum sup comprising uiegnd direct current; '.arhpliher-Theplato .Supply Yoltserfothe plato. T. ,is

developed .from as oohdarmwhdhg 1.28..,of. the transformer. 212-., @heterminale? the. Seconery 12B is Connectodthroueha oonrohtiohol rootihorelement ,1;29 thencey ,throlehe .resistance 130.110 the platey |21,Theother terminalofthe secondary winding 12.8 'is connected; through .ailtor Acaracter |31 'and thoroeto. tho plate. |21g f 'A p airofserially-connected resistances13 2 and |33 are connected as ableederacross the capacitor A second'filter network 135,. similar inarrangement tothe filternetworl; |11,;i s connected between a controlgrid |36 and a cathode 1 31-of the other half of the'dual-triode vacuumtube 12|?. The network |35 co mprises two serially connected capacitors138" and |39 connected inparallel with a resistance "14 ,Thel resistance14|is connected between the cathode 1 19 of y'the' rst half ofthedual-triode and the control grid 1330i the second half. "Ihus,A 'thevoutput Vfrom the-first'half of the dual-triode v'121) istaken fromthecathode 119. A resistance |42 is connected'between'the junction ofthecapacitors |38' and "1 39and the cathode |31 of Vacuum tube |20.

' The function of filter '|35 differs from that of the lter |11 inthat'lter |35 is adapted 'to reject or greatly attenuate 60rcycleripple.rather than 120 cycle ripple. lThis ripple originates fromthe power supply providingvoltage to the bridge input terminals 101'and|09. This 60 cycle ripple is amplied by the first half ofthe dualetriodevacuumtube 1'20"so"as to be" at a higherlevel than the directlcurrentcomponenth It therefore mustbe' attenuated vbefore it is appliedto the control grid 136'of the -second half of the tube in order thatthe"seclo'nd half 'of the tube may also act asaldirec'current amplifier.4 A- plate |43 of the" second half of the duali t'riode is connectedto asource-of potential by a lead 144 to the' bleederr`esistance""56connected across the output 'ofthe power'supply'fornied kby thetransformer 3 6 andthe duo-diode 09. The filaments H of the' Vacuumt'ubef |20 arespplied directly from a'secondary'lltoffthetransformefw-The end of the resistance 1'41j'connected`to the cathode` 1"1 El is alsoconnected through* aresistance 1l l1""to the secondary' winding 128' ofVthe which is connectedto the 'cathode '131jis vconnected 'alsoto thejunction' between the bleeder resistances 1321and'133rf'h potential ofthe cathode 1311's then at a iugiiefpositive potential than the controlgrid |36 and4 the tubeisy biased. As it is desirable'to furnish anegative'bias Voltage for arcont'rolgrid1 34vfof-theyacuum tube 5 8,apower supply to provide saidbiasing Vvolti eso provided said.powersupply Q Olhhrisos a secondary winding 158 of the transformer 92,one

terminal of said secondary being connected to one terminal ofa rectifier|59 similar to the rectifier |03. TheL other side ofthe rectifier |59 isconnected through a resistance |60 and a resistance |6|V` and thenceby alead |62 and the lead |48 to the control grid |34 of the vacuum tube 58.The Aother terminal of ,the secondary |58 is connected by a lead |63andthe lead |55 to the cathode 62 of the `vacuum tube 58. A capacitor|64 is connected between said last mentioned terminal and thejunction ofthe resistances |60 and|6| to cooperate withY the resistance |60 as afilter network to smooth out the rectifier ripple.

It is thus seen that the input to the first half of the vacuum tube |20isapplied between the grid ||8 and the cathode H3. The-output from thecathode ||9 is then applied to the filter |35 to eliminate 60 cycleripple and thence impressed between the control grid-'|36 and thecathode |31. This causes the Voltage at the cathode |31 to changeresulting in a change in the bias on the grid |34 of the vacuum tube 58.By Way of example, assume the output voltage tends tol rise. This causesthe filament 16 of diode 13 to increase in temperature with a resultingincrease in emission causing a decrease in the impedance of the diodeand a resulting unbalance in the bridge. This unbalance is manifested asa decrease in the potential of the terminal with respect to the-terminal||6.

As terminal l5 is connected to the grid I8 of vacuum tube and theterminal ||6 is connected to the cathode, the grid ||8 is made morenegative with respect to the cathode causing the current in theY tubetodecrease. As the cathode follows the grid, its potential likewise drops.Now, as the cathode ||9 is also connected through the resistance |4| tothe control grid |36 of the other half of the tube |20, the potential ofthe grid |36 will .also drop as will the potential of the cathode |31.As the cathode |31 is connected by a lead |48 through a resistance |43to the control grid |34 of the Vacuum tube 58, the potential of thecontrol grid |34 will also decrease.

Therefore, the plate current through the tube 58 is decreased with aresultant decrease in the current through the direct current winding 2|of the saturable core reactor 20. This causes an increase in theimpedance in the alternating current coils I8 and |9 and a concomitantdecrease in the magnitude of the alternating cur- E rent voltagevoutput.A decrease in the output voltage would cause the same cycle of eventsbut in the reverse direction.

A filter network |5| similar in arrangement to the filter networks ||1and |35 is connected between the grid |34 and the cathode 62 of thevacuum tube 58. The network |5| comprises tWo serially connectedcapacitors |52 and |53 connected in parallel with the resistance |49. Aresistance |54 is connected with the junction of the capacitors |52 and|53 and the cathode 62. This latter connection is made by a lead |55.Thus, the output Voltage from the cathode |31 of the tube |20 is appliedthrough the filter |5| to the grid-cathode circuit of the vacuum tube53. This filter prevents hunting which occurs when the control circuitovershoots. For example, if the output voltage rises, the controlcircuit may over-correct and this cycle will continue at a comparativelylow frequency, the value of which will depend upon the time constants inthe Various resistance capacitor combinations in the control circuit. Avfrequency of approximately 2.5 cycles is typical and hence if a filtercapable of n rejecting this frequency is placed across the gridcathodecircuit of the vacuum tube, hunting will not take place.

Another anti-hunting feature is provided by connecting a pair ofcapacitors |56 and |51 across the primary 31 of the transformer 36. Thecathode 62 of the vacuum tube 58 is connected to the junction of thecapacitors |56 and |51. When the circuit tends to overshoot and the grid|34 is being actuated in one direction, an alternating current voltageis applied to the cathode 62 yso as to counteract the overshoot of thegrid voltage.

Having thus set forth the nature of our invention, what we claim is:

l. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of `an alternating current voltage between predeterminedlimits, said regulator including an input circuit, transformer meanshaving a firstportion associated `with said input circuit, an outputcircuit connected with a second portion of said transformer means, asaturable core reactor having an alternating current portion and adirect current portion, means for alteringv the voltage across saidtransformer means and thereby the output circuit by varying theimpedance of said alternating current portion, a bridge circuit having adiode vacuum tube forming one of the arms thereof the filament of saiddiode being connected across said output circuit whereby a variation inthe outputvoltage varies the temperature of said filament to therebyimbalance said bridge, a direct current amplier, filter means associatedwith said direct'current amplifier, means for applying the output ofsaidbridge circuit through said filter means to said direct currentamplifier whereby said filter means is adapted to reject unwantedalternating current ripple which may be present in the output from saidbridge circuit, vacuum tube means, means for applying the output fromVsaid direct current amplifier to said vacuum Ytube means to control theplatecurrent thereof,`and means for applying said plate current to thedirect current portion of said saturable core reactor to r control theimpedance of said alternating current portion and to thereby maintainythe Voltage of y said output circuit within said predetermined limits. I

2. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of lan alternating current voltage between predeterminedlimits, said `regulator including an input circuit having the' primaryof an auto-transformer connected thereto, an output circuit associatedAwith the secondary of said autotransfonmer, a saturable core reactorhaving an alternating current portion anda direct current portion, meansfor altering the voltagegacross said transformer means and thereby theoutput circuit by varying the impedance of said alternating currentportion, a bridgecircuit having a diode vacuum tube forming one of thearms thereof, the filament of said diode being connected across saidoutput circuit whereby a variation in the output voltageyaries thetemperature of said filament to thereby unbalance said bridge, a directcurrent amplifier, filter means associated with said'direct currentamtransformer means; asaturable core reactor having analterna'tingcurrent portion anda dirctcurrentportion, 4means for altering the volt-vageacross Vsaid transformer meansl and thereby the output circuit by'Varying the' impedance of said alternating current portionfa bridge`circuit l havingv 'a'diode-vacuumtube Vforming one of the arnis thereofthe-'filament 'cfg said diode being cbnne'ctediacross"said outputcircuit whereby a variation irr'the 'output' lvoltage varies thetemperaturepf saldi filament' to "thereby"imbalance saidbridge, 'adirect''current amplifier, iilter means associated with saidz direct,current amplifer; rneans'ifor applyingthe output ofv said bridgecircuit' through `"said lternieans to-said direct currentamplier'ivhereby said filter means 'is adapted to "reject unwantedalternating current ripple' which 'maybe present ing' the output fromsaidibrid'ge" circuit, vacuurntubemeans having at least aplatefafcontrol: grida-nd4 a cathode, an anti-hunting"means,"v saidmeans comprising a filter network between said control grid and saidcathode'f i said; iilter -'network being' adapted to rejectv 'the'"frequency "at "which "said, regulator would tend to huntf'rneans forapplying the output "from "said, directf current; Vampliiier throughsaid anti-hunting means` to the control gridl of said:y vacuum'tub'emeans Vto control the plate current" th'ereofff-and'nneans; for applyingsaid platecurrentrto therdirectl current portion of saidl"saturable corereactor tol control 'the impedance'of said alternating current portionand to'"'thereby maintainthej voltage of,X said output circuit'withi'n"'said' predetermined limits.

41A highlyA accurate' 4electronic voltage regulator adaptedtouegulatethe' magnitude of an alternating `current voltage betweenpredeterminedflirni'ts, saidregulat'or including an input circuit,transformer means having aiirstpcrtion associatedwith 's'aid inputcircuit', an output cirn cuitconrecte'd:with'a secondportion of saidtransformer means, a saturable core reactor 'having analternatingrurrent portio'rrand a'direct current portionjmeans" for'laltering the voltage lacross said transformer means and thereby theoutput circuit byV` varying Ithe "impedance "of said altermating currentportion', a 'bridge circuit `having a diode-'vacuum tub'ewforming'oneofthe arms thereof the filament of'said diode being connected acrosssaid outputcircuit 'whereby' 'al variation in the output voltagevaries-thetemperature of'said filament "to th'erebyunbalance' rsaidybridge; a double "stage direct'lcurrent amplier having a rst Vacuumtube means and a 's'econdvacuum tube means; eachof"said"vacuum`"tube'means having" at reastaj plate, acathode andAcontrol Aa irstfillterv means connected between 'the id and cathode'ofsaid lirst Vacuum tube means, cond iilter"'rne'z'tns"c o'nr'iecteo'lythe'grid and "cathode 0f' Seid. Second Yaiuuel tube means,

bh 0f Said'futr fris, beins'adapted to attenuate separately alternatingcurrent ripple components superimposed on the output from said bridgecircuit, means for talringthe output from the cathode of saidrstvacuumtu'be means and applying it through said second ii'lterrneansto the controlr gridvof saidsecond vacuum 'tube means, athirdVacuum tubemeans'havingat least a plate, a cathode anda control grid, ananti-hunting means, said means comprising a lter network between saidlast mentioned controlgrid andcathode, saidfilter network being adaptedto reject thefrequency-atrwhich Ysaid regulator would -tend to hunt;means for taking the output from the Acathode of Vsaidv second vacuumtube means through f said anti-hunting means to the control-'grid vofsaidthird Vacuum tube means to control the'plate current thereof, andmeans for applying saidplate currentto the direct current portion ofsaid saturable core reactor yto controlV the impedance of saidalternatngzcurrent portions' and to thereby maintain the voltage of saidyoutputfcircuit Within saidl predetermined'limits.vv v I f f v- 5.Ahighly accurate electronic voltage regulator adapted to regulate-fthemagnitude ofv an alternating' current' voltage-betweenpredetermined limitssaid regulatorV including an input circuit,transformer means-having a rst portion associated with said inputcircuit, an output 'circuit connected vwith asecondf portion offsaidtransformer means, a saturablecore reactor having anl alternatingcurrentY portion anda direct current portion; means for altering thevoltage across said transformer means andtherebythe output circuit byAv'aryingthe impedanceof said alternating current portion, al bridgecircuit having a diode 'vacuum tube forming one ofthe arms thereof thenlament of said diode being connected across said output circuitv'fherebyia Variation in the output voltage Varies" the temperatureof'said filament to 'thereby' -unbalance said bridge, a double stagedirect "current amplier having a r'styacuum' tube `-means"'and a second'vacuum tube means, each of "saidfvacuumttube Vmeans having at least-"aplate, v` a' 'cathode andi a control grid, a first iilter means:connected between the grid and cathode ofsaidrs'tvacuum tube means, asecond lter'means' connectedbetween'thegrid and cathode of saidsecond'vacuumtube means, each of said filter meaxisbeing'adaptedtoattenu'ate separately'alt'ernating "current "ripplecomponents"superimposedv otheV Voutput from said bridge'circuitfmeansfortakingthe output from the cathode of said 'first' vacuum tube means andapplying it through'saidsecond filter"means to the control grid" of said"secondva'cuum tube means, a third Vacuum"tube'mearls` having'at least aplate, 4a cathode and a'control grid, va nrst anti-hunting means, saidmeans' comprising a lter network between'said last mentioned VcontrolYgrid'v and cathode," said filter networkH being adapted" to' reject Ythefrequency at' whi'ch'sai'd regulator would tend"to`hunt,`ineans'fortaking the output from the cathode Yofl'said second vacuuin "tubemeans through said'nrst lanti-hunting means to the"v contr'olf grid 'efl said t'third vacuum rable core reactor to control the impedance ofsaid alternating current portion to thereby maintain the voltage vofsaid'output circuit within said predetermined limits. Y

6. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator including an input circuit having the primary ofan auto-transformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a saturable core reactor havingan alternating rcurrent portion and a direct current portion, means foraltering the voltage across said output circuit by Varying the impedanceof said alternating current portion, a bridge circuit having a specialdiode forming one of the arms thereof, said special diode having an armadapted to short the diode plate to its filament in the event saidlament burns out, the filament of said diode being connected across saidoutput circuit whereby a variation in the output voltage varies thetemperature of said filament to thereby imbalance said bridge, a doublestage direct current amplifier having a iirst vacuum tube means and asecond vacuum tube means, each of said vacuum tube means having at leasta plate, a cathode anda control grid, a first filter means connectedbetween the grid and cathode of said first vacuum tube means, a secondfilter means connected between the grid and cathode of said secondvacuum tube means. each of said iilter means being adapted to attenuateseparately alternating current ripple components superimposed on theoutput from said bridge circuit, means for taking the output from thecathode of said iirst vacuum tube means and applying it through saidsecond filter means to the control grid of said second vacuum tubemeans, a third vacuum tube means having at least a plate, a cathode anda control grid, an anti-hunting means, said ,means comprising a filternetwork between' said last mentioned control grid and cathode, saidfilter network being adapted to reject the frequency at which saidregulator would tend to hunt, means for taking the output from thecathode of ,said second vacuum tube means vthrough said anti-huntingmeans to the control grid of 'said third vacuum tube means to controlthe plate current .Y

power supply adapted to supply direct current voltage to said bridgecircuit, one side of the primary winding of each of said transformersbeing connected to one lead of said output circuit, the other side ofeach of said primaries being connected to one of a pair of vacantterminals on the usual tube socket associated with said special diode,the other of said pair of terminals being connected to the other lead ofsaid outputcircuit, a strap across the vacant terminals on said specialdiode which engages with the aforementioned pair of vacant terminals onsaid usual tube socket when said diode is in said socket whereby undersuch condition the primaries of said iirst and second transformers areconnected `across said output circuit but in the event said diode isremoved said transformers are disconnected from said output circuit toprevent the voltage across said output from exceeding the predeterminedvoltage and thereby preventing damage to apparatus supplied from saidvoltage regulator, and

- limits.

7. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator including an input circuit having the primary ofan auto-transformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a saturable core reactor havingan alternating current portion and a direct current portion, means foraltering the voltage across said output circuit by varying the impedanceof said alternating current portion, a bridge circuit having a diodevacuum tube forming one of the arms thereof, the filament of said diodebeing connected across said output circuit whereby a variation in theoutput voltagevaries the temperature of said filament to therebyuribalance said bridge, a direct current ampliiier, iilter meansassociated with said direct current amplifier, means for applying theoutput of said bridge circuit through said filter means to said directcurrent amplifier whereby said iilter means is adapted to rejectunwanted alternating current ripple which may be present in the outputfrom said bridge circuit, vacuum tube means having at least a plate, acontrol grid, a cathode and a lament, an anti-hunting means, said meanscomprising a filter network between said control grid and said cathode,said filter network being adapted to reject the frequency at which saidregulator would tend to hunt, means for applying the output from saiddirect current amplifier through said anti-hunting means to the controlgrid of said vacuum tube means to control the plate current thereof, afirst filament transformer for supplying current to said filament, theprimary of said first filament transformer being connected across saidoutput circuit, a booster lament transformer for supplying current tosaid filament, the primary of said booster transformer being connectedacross a lead of said input circuit and a lead of said output circuit,the secondary of said booster transformer being connected in series withthe secondary of said first filament transformer, the sum of thevoltages across said secondaries being applied to said filament wherebyunder heavy initial loads a voltage appears across the primary of saidbooster transformer to thereby supply additional voltage to saidfilament enabling said filament to heat sufficiently to allow saidregulator to function and upon functioning no voltage appears acrosssaid booster transformer, and means for applying the plate current ofsaid vacuum tube means to the direct current portion of said saturablecore reactor to control the impedance of said alternating currentportion and to thereby maintain the voltage of said output circuitwithin saidpredetermined limits.

8. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator including an input circuit, transformer meanshaving a iirst portion associated with said input circuit, an outputcircuit connected with a second portiony of said transformer means, asaturable core reactor having an alternating current portion and adirect currentportion, means for-- alteringA the Voltageacross saidtransformer means andthereby the output circuit by Avarying theimpedance` of said alternating current portion, akbridge circuit havinga diode vacuum tube forming one ci the arms thereof the filament of saiddiode being connected across said output circuit whereby a variation inthe output voltage varies the temperature of said filament to thereby`unbalance said bridge, a double stage direct current amplifier having afirst vacuum tube means and a second vacuuml tube means, each of saidvacuum tube means having at least a plate, a cathode and a control grid,a first lilter means connected betweenA the grid and cathode of saidfirst vacuum tube means, a second iilter means connected between` thegrid and cathode of said second vacuum tube means, each of said ltermeansv being;r adapted to attenuate separately alternatingcurrentripplercomponents superimposed on the output lfrom said bridgecircuit, means for taking-the. output from the cathode of` said rstvacuumtube means and applying it through said second iilter'means tothecontrol grid of said second vacuum tube means, a third vacuum tubemeanshaving; at least a plate, a control grid, av cathode andV afilament, an anti-hunting means, saidy means comprising a filter networkbetween said control grid and said cathode, said filter network beingadapted to reject the frequency at whichv said regulator would tend tohunt, means for applying the output from said direct current amplifierthrough said anti-hunting means to the control grid of said vacuum tubemeans to control the plate current thereof, a iirst lament transformerfor supplying current to saidV filament the primary of said firstfilament transformer being connected across said output circuit, abooster filament transformer for supplying currentY to said nlament, theprimary of said booster transformer being connected across a lead ofsaid input circuit and a lead of said output circuit, the secondary ofsaid booster transformer beiner connected in series with the secondaryof' said first nlament transformer, the sum of the volt- A' ages acrosssaid secondaries beingapplied tosaid lament whereby under heavy initialloads a voltage appears across the primary of saidbooster transformer tothereby supply additional voltage to said filament enablingl saidfilament to heat suiiiciently to allow said regulator to function andupon functioning no voltage armeens` across said booster transformer,and means for applying the plate current of said vacuum tube means tothe direct current portion of said saturable core reactor to control theimpedance of said alternating current portion and to thereby maintainthe voltage of said output circuit within said predetermined limits.

9. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator including an input circuit having the primary ofan autotransformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a saturable core reactor havingan alternating current portion and a direct'current portion, means foraltering the voltage across said output. circuit by varying thevimpedance of said alternating current portion, a bridge circuit having aspecial diode forming. one of the arms thereof, said special diodehaving an arm adapted to short the diode plate to its lilament in theevent said filament burns out, the filament efeeiddiedebeine;-eenileetedeereseseid output eireuit, whereby a varietienntheOutput. Voltage varies the .temperature Qtseid fllementte. therebyunbalance'said bridge, a double .stagerdirect cur# rent.v ampler having,al'ret veeuw' tubemeene @Qd .ai SBCQHQ. Vaclliullitllbe 319335 earch;0iA Said, vacuuml tube means having" at. leastf a platea Cathode; and;a, Control grid. e tiret ltermeent eonneetedbetweenrtheerdpendeethedesef Seid rst vaeuumtube. means e Second filter meanseonneetedibetween-the.gridieridieethede 0f Seid seeendvacuum. tube.-meenef, each. ef; Seid lter mea-.ris beine adapted` te attenuate..Separately alternating current.: rippleA componente.. Seperiie nosed.;`01.1A the Outputl from; Seid. bridge; erilit means.. for taking: theOutput from., the, eethede Oi'. Said'. lSl?. VaQlllllP-tub 1113.335 am@applying it, through said second nlter means tol thev conftro1..grid.0f;seid Seeendsreellem tube meent., el thirdvaeuuni tube,means harige etleeet. er plete., a cathode and. a; eeritrel` grida enanti-hunting means, said means c9mprising, a filter network; betweenSaid, lest: mentened Qontrol. grden@ cathode, saisi; filter` netwerk;beine adapted-t0 reject the frequency atwhich said regulatorwouldstendtehuntf menester: taking the Output from. the: cathode QfSaid; seerld. Vacuum; time means through` eadentifhuetns; meent.,11e-the control grid of sai/d third v acu-umtube means te` control the.pleteeerrestthereet a tetftrelsformer forminglv aV portion o -f-A apower supply adapted to supply direct current voltage* toA said thirdvacuum tube means, aksecond transformer forminee Dertien off e newer.-Surely-adapted@ supplydirect current voltageto said bridge cir'l Cuit,011e eide 0f theprmerrwindme ef eeen ef said transformers beingAconnected to4 one lead of said output circuit, the othersideoi each ofsaid primaries being connected to one ofl al pair of vacant-terminals onthe usual tube socket as-` sociated with said specialdiopde, the otherof said pair of terminals being connected to the other lead of saidoutput circ-uit, a strap across the vacant terminals on said specialdiode which engages with the aforementioned pair; ofvfvvac/ant terminalson saidV usual tube socket whensaid diode is in said socket wherebyunder such condition the primaries of-- said first and secondtransformers are connected across said output circuit but in the eventsaid diodel is removed said transformers arel `d iscormecte'd from saidoutput circuit to prevent thevoltagev across said output from exceedingthepredetermined voltage and thereby preventingdamageto apparatussupplied from said voltage regulator, a rectifier associated with asecondaryv of said second transformer to supply direct current to saidbridge, a plurality of gas-nlled electronic tubes connected across theoutput of said rectiiier to regulate the voltage applied to said bridge,lter means connected across said output circuit to remove third andfifth harmonic distortion and means for applying the plate current ofsaid third vacuum tube means through the direct current portion of saidsaturable core reactor to control the impedance of said alternatingcur-rent portion to thereby maintain the Avoltage of said output circuitwithin saidk predetermined limits.

10. A highlyv accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator. including an input circuit having the primary ofan autortransformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a saturable core reactor havingan alternating current portion and a direct current portion, means foraltering the voltage across said output circuit by varying the impedanceof said alternating current portion, a bridge circuit having a diodevacuum tube forming one of the arms thereof the iilament of said diodebeing connected across said output circuit whereby a variation in theoutput voltage varies the temperature of said filament to therebyimbalance said bridge, a double stagev direct current vampliiier havinga first vacuum tube means and a second vacuum tube means, each of saidvacuum tube means having at least a plate, a cathode and a control grid,a rst lter network connected between the grid and cathode of said firstvacuum tube means, said filter network comprising a pair of seriallyconnected capacitors connected in parallel with a rst resistance, oneend of said first resistance being connected to the grid of said rstvacuum tube means, the other end of said first resistance beingconnected to an output terminal of said bridge, a second resistancehaving one end connected to the junction of said serially connectedcapacitors, the other end being connected to the cathode of said firstvacuum tube means, said iilter network being adapted to reject acomponent alternating current ripple appearing on the output voltagefrom said bridge, a second iilter network connected between the controlgrid and cathode of' said second vacuum tube means, said second filteralso comprising a pair of serially connected capacitors connected inparallel with a first resistance, one end of said last mentioned iirstresistance being connected to the control grid of said second vacuumtube means, the other end being connectedv to the cathode of said firstvacuum tube means, a second resistance having one end connected to thejunction of the serially connected capacitors of said second lternetwork, the other end being connected to the cathode of said secondvacuum tube means, said second iilter network being f adapted to rejecta component alternating current ripple appearing on the output voltagefrom the cathode of said iirst vacuum tube means, a third vacuum tubemeans having at least a plate, a cathode and a control grid, anAanti-hunting means, said means comprising a filter network between saidlast mentioned control grid and cathode, said iilter network beingadapted to reject the frequency at which said regulator would tend tohunt, means for taking the output from the cathode of said second vacuumtube means through said anti-hunting means to the control grid of saidthird vacuum tube means to control the plate current thereof, and meansfor applying said plate current to the direct current portion of saidsaturable core reactor to control the impedance of said alternatingcurrent portion and to thereby maintain the voltage of said outputcircuit within said predetermined limits.

11. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage` between predeterminedlimits, said regulator including aninput circuit having the primary ofan auto-transformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a lead of said input circuitbeing common with a lead of said output circuit, a satura-ble corereactor having an alternating current portion and a direct currentportion, said alternat- 7;5

ing current portion being connected in series with the lead common tosaid input circuit and said output circuit, an inductance and acapacitance in series therewith, said combination being connected acrosssaid output circuit to remove iifth harmonic distortion from saidoutput, a second inductance and a capacitance in series therewith, saidsecond combination likewise being connected across said output circuitto remove third harmonic distortion from said output, a third inductanceconnected across said output circuit to inductively load said outputcircuit, a bridge circuit having a diode vacuum tube forming one of thearms thereof the iilament of said diode being connected across saidoutput whereby a variation in the output voltage varies the temperatureof said iilament to thereby unbalance said bridge, a double stage directcurrent ampliiier having a rst vacuum tube means and a second vacuumtube means each of said Vacuum tube means having at least a plate, acathode and a control grid, a iirst iilter network connected between thegrid and cathode of said first vacuum tube means, said filter networkcomprising a pair of serially connected capacitors connected in parallelwith a iirst resistance, one end of said first resistance beingconnected to the grid of said first vacuum tube means, the other end ofsaid rst resistance being connected to an output terminal of saidbridge, a second resistance having one end connected to the junction ofsaid serially connected capacitors, the other end being connected to thecathode of said rst vacuum tube means, said filter network being adaptedto reject a component alternating current ripple appearing on the outputvoltage from said bridge, a second lter network connected between thecontrol grid and cathode of said second vacuum tube means, said secondfilter also comprising a pair of serially connected capacitors connectedin parallel with a rst resistance, one end of said last mentioned firstresistance being connected to the control grid of said second vacuumtube means, the other end being connected to the cathode of said firstvacuum tube means, a second resistance having one end connected to thejunction of the serially connected capacitors of said second filternetwork the other end being connected to the cathode of said secondvacuum tube means, said second filter network being adapted to reject acomponent alternating current ripple appearing on the output voltagefrom the cathode of said iirst vacuum tube means, a third vacuum tubemeans having at -least a plate, a cathode and a control grid, an

anti-hunting means, said anti-hunting means comprising a filter networkbetween the control grid and cathode of said third vacuumY tube means,said filter network being similar in arrangement to said rst filternetwork and said second iilter network and comprising a pair of seriallyconnected capacitors in parallel with a first resistance, one end ofsaid first resistance being connected to the cathode of said secondvacuum tube means the other end being connected to the control grid ofsaid third vacuum tube means, a second resistance having one endconnected to the junction of the last mentioned serially connectedcapacitors, the other end being connected to the cathode of said thirdvacuum tube means, said anti-hunting means being adapted to reject thefrequency at which said regulator would tend to hunt, a connection fromthe plate of said third vacuum tube vmeans to the direct current portionof said saturable core reactor whereby the impedance of said alternatingcurrent portion is variedin accordance with the plate current throughsaid direct current portion to thereby maintain the voltage of saidoutput within said predetermined limits.

12. A highly accurate electronic voltage regulator adapted to regulatethe magnitude of an alternating current voltage between predeterminedlimits, said regulator including an input circuit having the primary ofan auto-transformer connected thereto, an output circuit associated withthe secondary of said auto-transformer, a saturable core reactor havingan alternating current portion and a direct current portion, means foraltering the voltage across said output circuit by varying the impedanceof said alternating current portion, a bridge circuit having a diodevacuum tube forming one of the arms thereof, the lament of said diodebeing connected across said output circuit whereby a variation in theoutput voltage varies the temperature of said lament to unbalance saidbridge and vary the output thereof, an amplier connected with the outputof said bridge, a second vacuum tube having at least a plate, a cathodeand a control grid, means for applying the output of said amplifier tosaid control grid, a first transformer forming a portion of a powersupply adapted to supply direct current voltage to said second vacuumtube, a second transformer forming a portion of a power supply adaptedto supply direct current voltage to said bridge circuit, one side of theprimary winding of each of said transformers being connected to one leadof 18 mined limits, said regulator including an input circuit,transformer means having a first portion associated with said inputcircuit, an output circuit connected with a second portion of saidtransformer means, a saturable core reactor having an alternatingcurrent portion and a direct current portion, means for altering thevoltage across said transformer means and thereby the output circuit byvarying the impedance of said alternating current portion, a bridgecircuit having a diode vacuum tube forming one of the arms thereof thefilament of said diode being connected across said output circuitwhereby a variation in the output voltage varies the temperature of saidfilament to thereby unbalance said bridge, a plurality of variableresistors, switch means for selectively connecting said resistors in thelament circuit of said diode whereby the filament current may be variedto adapt the circuit for operation over a wide range of desired outputvoltages, a direct current amplier, lter means associated with saiddirect current amplier, means for applying the output of said bridgecircuit through said filter means to said direct current amplifierwhereby said lter means is adapted to reject unwanted alternatingcurrent ripple which may be present in the output from said bridgecircuit, vacuum tube means, means for applying the output from said'direct current amplier to said Vacuum tube means to control the platecurrent thereof. and means for applying said plate current to the directcurrent portion of said saturable core reactor to control the impedanceof said alternating current portion and lto thereby maintain the voltageof said output circuit Within said predetermined limits.

ALLEN K. BROWN. ADOLPH O. BUNBLASKY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,472,167 Matson -et al. June 7,1949 2,569,500 Sorensen Oct. 2, 1951

